Case IH 3870 (DTC 936B) - ECU – Engine Control Unit (ECU) and Vehicle Controller: BC2ECU1 message

This code indicates a CAN communication failure between the vehicle controller and the ECU. The system has lost the critical data link required for the engine and the main vehicle controller to communicate properly.

• MAXXUM T4E
• 240 Series Axial-Flow Combines
• 7240
• 8240
• 9240

1. 1

   Check for related CAN faults: Verify if there are other active CAN bus faults (such as DTC 951B 'CAN A Bus off failure' or DTC 93CB 'TSC1_VR message'). If other CAN faults exist, they must be resolved first, as a single shorted module can take down the entire network.

2. 2

   Check ECU Supply Voltage: Disconnect the vehicle (VE) harness from the ECU A-095 at connector X-911. Turn the ignition switch to the ON position and use a multimeter to check for proper voltage on the vehicle harness.

3. 3

   Inspect Power Systems: Rule out external power supply issues, a faulty charging system, or a faulty solenoid that could be causing voltage drops or electrical interference.

1. 1

   Verify Voltage

   Perform the voltage test at connector X-911 as described above. Ensure the battery and charging system are operating within normal parameters.

2. 2

   Inspect the Wiring Harness

   Thoroughly inspect the CAN bus wiring harness running between the Vehicle Controller (CCU/UCM) and the Engine ECU. Look for chafed wires, open circuits, or short circuits.

3. 3

   Check Connectors

   Inspect connector X-911 and the connectors at the CCU for pushed pins, corrosion, or moisture intrusion.

4. 4

   Isolate Solenoids

   Because a faulty solenoid can short the system, temporarily isolate suspect solenoids to see if CAN communication is restored.

5. 5

   Replace/Reprogram Modules

   If the wiring harness, power supply, and connectors all test good, the communication failure is likely internal to either the Central Control Unit (CCU/UCM) or the Engine ECU. The faulty module will need to be replaced and flashed with the latest software by an authorized dealer.